Mario Bonsembiante

Quanti-qualitative evaluation of pectins in the dietary fibre of 24 foods

Abstract The dietary fibre of 24 foods was analysed for its proportions of insoluble and soluble (SDF) fractions and for its content of high methoxyl pectins (HM), low methoxyl pectins (LM) and protopectin. The fractional extraction and quantitative determination of pectins were performed on the total dietary fibre residue, following the procedure suggested by Robertson (1979). Total pectin content (TP), calculated as sum of the three fractions, ranged from 2.4 to 49.8 g/kg of dry matter. The variation coefficient of TP measurements repeated on the same foods were, on average, 2%. Total pectin content was 49.8 g/kg DM in dried beet pulp and averaged 33.8±0.3 g/kg DM in fruits and vegetables, 13.2±8.4 g/kg DM in legumes and tubers and only 2.8±0.5 g/kg DM in cereals. HM fraction prevailed in apple and pear samples (>40% of TP), while LM and protopectin largely prevailed in legumes and vegetables. A strong variability among foods was found for the TP/SDF ratio. In general, within each food category, increasing levels of SDF were associated with decreasing values of TP/SDF ratio. Since many foods contain low amounts of pectins, care in the development of calibration curves for spectrophotometric reading is required. Finally, the whole procedure for pectin extraction and quantification on dietary fibre of food is very complex and time-consuming.

Fattening Performance and Slaughter Traits of Purebred and Crossed Young Bulls

In order to evaluate the effect of crossing beef bulls with dual-purpose cows on the performance of fattening young bulls, a trial was carried out on 74 calves of the following genetic types: Italian Brown Swiss (IBS), German Simmental (GS) and crosses obtained from Piedmont (PD x IBS and PD x GS)Limousin (LM x IBS and LM x GS) and Charolais (CH x GS) bulls.

Estimation of the content of pectins in feeds: Fractional extraction and quantitative determination

Pectic substances, found in the primary cell wall and middle lamella of the plant tissues as complex polymers of galacturonic acid, play an important nutritional role in the gastrointestinal tract. Their dietary function is due to their physical properties, which include the ability to form gels, to build cations and to increase the waterholding capacity (Voragen et al., 1995, 2001). These physical characteristics are dependent on the substances’ chemical structure and, consequently, pectic substances are fractionated into HM pectins (high-methoxyl pectins), LM pectins ( low-methoxyl pectins) and protopectin (Thibault and Ralet, 2001). Must studies have been carried out on fruit because the ripening process induces a modification of the amount of total pectins (TP) and also of the ratio among the three fractions (Robertson, 1979). Moreover, the additives employed in the food industry are usually obtained from apple or citrus extraction (Thibault and Ralet, 2001). The purpose of this preliminary work is evaluation of the fractional extraction procedure and quantitative determination of total pectic substances of different feeds.